In electrical control systems for airplanes it is necessary to provide for selective energization of a large number of electrical controllers for controlling or positioning of electrical loads such as the landing gear, flight control surfaces, actuators, etc. These loads include elements located at various remote places throughout the airplane, as in the wings, tail, etc., and the manual control switches for the devices is generally located at the flight control station in the pilot's cabin. In the co-pending U.S. Pat. application Ser. No. 755,557, filed Dec. 30, 1976, entitled "Electric Power System Control Utilizing Low Level Signals and Miniature Gauge Wiring" filed concurrently herewith and hereby incorporated herein by reference, a system for such control is disclosed in which a direct current, low power supply buss at the flight control station is connected to each of a plurality of control circuit switches through a separate current limiting warning light (CLWL). The control switches are individually operative to impress a low level operating signal on a small gauge control conductor extending to a solid state/relay circuit or a solid state power controller (SSPC) at each load position. The low level signals may control a relatively high power relay at an SSPC to energize the corresponding load device from a high power supply buss. In an aircraft environment, the CLWL's are preferably unlighted both when the corresponding control circuit switch is inoperative and when it is operated to close a power device circuit which is in normal operating condition. However, the solid state controller includes means responsive to fault conditions to open the power circuit and also to clamp the control conductor to ground potential. Grounding of the control conductor acts through the control circuit switch to ground the associated terminal of the CLWL significantly increasing the current flow therethrough. The resulting incandescence provides the necessary warning of a circuit fault or other malfunction.
In another co-pending U.S. Pat. application, Serial No. 755,560, filed Dec. 30, 1976, entitled "Solid State Power Controller With Low Level Signal Control" filed concurrently herewith and hereby incorporated herein by reference, a control system is disclosed for aircraft loads employing solid state power controllers without requiring associated electromechanical power relays and conventional overcurrent protection. This latter system also employs low level control circuits extending between the flight control station and the controllers at the load stations, and utilizes a CLWL type control arrangement as discussed above.
In the prior control systems, as well as those described in the two aforementioned applications, disconnection of non-essential loads can be accomplished by individual isolation of the loads through opening of their control circuits or the relays. Also, it is conventional to isolate non-essential loads by means of an extra "disconnect" buss to which such loads are connected. This, of course, has the disadvantage of requiring an increase in the number of power busses required in the airplane.
It accordingly is an object of the present invention to provide a novel method and system for permitting simultaneous disconnection of a preselected group of load devices in an electrical load control system.
It is another object of the present invention to provide a novel method and system whereby a plurality of preselected non-essential loads can be dropped simultaneously without requiring the use of additional load busses and solely through action on the low level control circuit system. The disconnection may be attained by a single manual operation or automatically in response to conditions occurring in the generator or load circuit. The arrangement may include the use of a separate programmable wiring device that selects the loads to be dropped. Different wire programs may be substituted to provide different load selections. Use of parallel logic in the disconnect arrangement avoids a need for series breaks and many interlock contacts such as are normally found in the circuits of the airplane load control system.
Other objects and advantages of the present invention will become apparent from the claims and from the following description when read in connection with the attached drawings.